linux-kernel - Re: [PATCH v2 3/3] x86/boot: Implement early memory acceptance for SEV-SNP

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Message-ID: <CAMj1kXGWPopQupteK0=mqd5z29Oj4Ye6KyPfgup-nHQO863Qow@mail.gmail.com>
Date: Mon, 7 Apr 2025 19:21:17 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
	Dionna Amalie Glaze <dionnaglaze@...gle.com>, Ard Biesheuvel <ardb+git@...gle.com>, linux-efi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, x86@...nel.org, 
	Tom Lendacky <thomas.lendacky@....com>, Borislav Petkov <bp@...en8.de>, 
	Kevin Loughlin <kevinloughlin@...gle.com>
Subject: Re: [PATCH v2 3/3] x86/boot: Implement early memory acceptance for SEV-SNP

On Mon, 7 Apr 2025 at 18:44, Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> wrote:
>
> > On Fri, Apr 04, 2025 at 08:07:03AM -0700, Dionna Amalie Glaze wrote:
> > > If the GHCB is available, we should always prefer it.
> >
> > I believe we should consider the cost of code duplication in this
> > situation.
> >
> > If the non-early version is only used in the kexec path, it will not be
> > tested as frequently and could be more easily broken. I think it would be
> > acceptable for kexec to be slightly slower if it results in more
> > maintainable code.
>
> Absolutely so.
>

It would be nice if someone could quantify 'slightly slower' - I am
leaning to the same conclusion but I have no clue what the actual
performance impact is.